Three Interstate highways, I-10, I-15 and I-40, enter southern California from Arizona and Nevada, carrying traffic to and from greater Los Angeles. I-40 ends in Barstow, joining I-15 which winds its way through the Cajon Pass and traverses the "Inland Empire", the Riverside-San Bernardino-Ontario metropolitan area directly east of LA and the 13th-most populous metropolitan area in the United States. Drivers traveling in or out of Southern California must not only navigate the congested environs of the Inland Empire, but they must also pass through the Devore Interchange, where I-15 and I-215 meet in the City and County of San Bernardino.

Severe delays are commonplace, with 5-mile backups typical during peak afternoon and weekend hours, as more than 1,000,000 vehicles squeeze through the Devore Interchange every week. This includes 21,000 trucks daily, part of a massive movement of freight into and out of Southern California through this nationally significant primary goods movement corridor. The interchange is also a major route to recreation destinations such as Las Vegas and the Colorado River. Therefore, the goal of the $324 million Devore Interchange Project is reduction of congestion and accidents, while providing significant improvement of freeway operation.

A highway design-build (DB) pilot program was authorized by the California legislature in 2009 and the California Department of Transportation (Caltrans) selected Devore as one of 15 projects to test this project delivery system. Seeking relief from the paralyzing dysfunction at the intersection of I-15 and I-215, Caltrans sought the same advantages realized by other states on hundreds of DB projects:

Awarded to Atkinson Construction (Irvine) in 2012 for scheduled completion in 2016, the $208 million construction contract adds one lane in each direction, builds 18 bridges, adds a truck bypass lane in each direction to eliminate weaving and improve overall safety, and reconnects Cajon Boulevard, the alignment of Historic Route 66 that was severed by the original interchange construction in the 1970s. Atkinson’s design called for 10 mechanically stabilized earth (MSE) walls totaling nearly 128,000 sq. ft., some of which face Cajon/Route 66 and required a high quality and visually appealing aesthetic treatment. This requirement was met by using a "New England Dry Stack" simulated stone facing panel finish, punctuated on longer walls by intermittent columns of smooth, raised finish panels (Fig. 1).

Based on previous successful Southern California project partnerships with The Reinforced Earth Company (RECo), Atkinson asked RECo to design and supply Reinforced Earth® MSE walls for the Devore Interchange. By doing so, Atkinson helped Caltrans achieve the advantages it sought from using design-build:

• Better Quality – RECo specializes in working as part of a DB team to provide customized designs that innovatively meet project engineering and productivity requirements. While anyone can design a wall that is long enough, high enough and has enough soil reinforcements, RECo’s designers work hand-in-hand with the DB contractor to develop designs that also optimize constructability while minimizing the cost of construction. Steeply stepped foundations (Fig. 2) require careful work at first, but pay off quickly through reduced excavation, less buried wall, and by allowing the contractor to rapidly achieve a longer, more productive stretch of wall to work on. And the square-shape Reinforced Earth facing panels were cast on a form liner, assuring a high quality finish and visual consistency from wall to wall.

• Faster Delivery – the in-house designers and project managers at RECo control every aspect of MSE wall design, fabrication and delivery, allowing seamless flow of approved designs directly into production of reinforcements and facing panels. RECo’s long-time precaster, Harper Precast, had extensive experience with Reinforced Earth products, assuring timely and trouble-free production. Though located in Salt Lake City, Harper’s 637-mile delivery distance was only a one-day straight shot down I-15 right to the jobsite.

• Cost Savings – on a design-build project time is money, and Atkinson’s design optimization process saved both. Using Reinforced Earth retaining walls helped achieve a 10% reduction in earthwork cuts and eliminated several embankment slopes, saving construction time and dollars. Onsite backfill was suitable for MSE wall construction, eliminating the cost to acquire and deliver imported borrow. And the speed of Reinforced Earth wall construction helped shorten the project schedule. In addition, both monetary and social costs were reduced by the extensive use of MSE walls, which contributed to reducing acquired right-of-way by 12 acres and 8 private residences.

• Singular Responsibility – according to Caltrans, "singular responsibility" in DB means one entity is accountable for cost, schedule and performance. That exactly describes The Reinforced Earth Company, which was solely responsible to design, manufacture and timely deliver its MSE walls on the schedule set forth by Atkinson Construction. RECo even provides its own project manager to help the contractor learn the best Reinforced Earth construction procedures applicable to the project.

• Reduced Risk – while the design-build team assumes additional risk compared to the design-bid-build method, the team also has complete control of that risk. RECo’s singular responsibility for MSE wall design and proven performance record of timely delivery and knowledgeable field service actually reduced the DB team’s risk.

Reduced risk, high quality, fast and reliable delivery and lower cost – and all from a single entity experienced in being responsible to accomplish it all. That’s what Atkinson Construction was looking for when they partnered with The Reinforced Earth Company and, as this story is being written, Atkinson is getting what they asked for. With Reinforced Earth wall construction nearing completion, and overall project completion just around the corner, drivers move ever closer to realizing the benefits of Caltrans’ design-build pilot program: smoother and faster traffic flow in the upgraded and beautified Devore Interchange in Southern California’s Inland Empire.